Reference interval and upper decission limit for serum uric acid – an evidence-based approach on Romanian population using an a posteriori method

Abstract

Introduction. There is accumulating evidence that high normal serum uric acid (SUA) levels of 6-7 mg/dL are associated with cardiovascular morbidity and metabolic syndrome (MetS), hence the need to redefine its upper limit of normal (ULN). We aimed to derive ULN based on statistics and evidence in a representative sample of the population and to observe its relation to MetS components. Methods. All SUA measurements form a university rheumatology hospital were extracted between January 5th 2010 and March 21st 2018. SUA levels were measured by a single biochemist a unique type of commercially available kit. Follow-up measurements, patients with diagnoses influencing SUA levels and outlying measurements were excluded. ULNs were studied using least square analysis. Results. Of the 22503 SUA measurements in the database, only 3318 came from normal individuals: 33.3% men (n=1105), 66.7% women (n = 2213). Least square analysis revealed the following SUA reference intervals (RI): 3.43-6.19 mg/dL for the combined sample; 4.44-7.01 mg/dL for men, 3.28-5.56 mg/dL for women. The values corresponding to the 66th percentile of each group presented lower ULNs: 5.36 mg/dL for all, 6.10 mg/dL for men, 4.90 mg/dL for women. The prevalence of hyperuricemia increased from 13.8% (manufacturer’s gender-specific ULN) to 19.9% (derived ULN). Mean SUA levels significantly increased with the number of MetS components. Conclusion. We recommend that hyperuricemia should be defined using a statistical approach of ULN selection corresponding to the genderand population-specific 66th percentile of data range.

Laboratory medicine in the era of precision medicine – dream or reality?

“…This is the main reason which caused alternative methods to be found and indirect methodologies to be encouraged by IFCC Committee on Reference Intervals and Decision Limits (8). Starting 2013, the Romanian Journal of Laboratory Medicine has published several articles proposing Hoffmann technique (9, 10) for determinations of reference intervals for hemoglobin, serum total magnesium and calcium in Romanian children (11,12), and decision limits for serum uric acid associated with cardiovascular morbidity and metabolic syndrome in this issue (13). On the other hand, by using the reference ranges concept for interpretation of test results there is a grey area where superposition of values from healthy and ill subject exists.…”